Engine Problems Still Cloud F-35 Progress

The SubSonex JSX2 is powered by the PBS T1-100 turbojet engine and has a range of about 500 nm, consuming some 18 gph on average.

Lockheed Martin (LM) staged a ceremonial rollout of the first two F-35A Lightning II stealth fighters for the Royal Australian Air Force (RAAF) on July 24 at Fort Worth, Texas. However, flying restrictions remain in force for the entire fleet, following the engine fire that grounded the type for 12 days in mid-month and prevented the aircraft’s international debut in the UK Meanwhile, contract negotiations for the eighth batch of low-rate initial production (LRIP) aircraft are taking longer than expected, and the UK is still not ready to sign for its first squadron of 14 aircraft.

The RAAF jets are designated AU-1 and AU-2. They will be delivered to Luke AFB later this year, where the RAAF already has an advance party setting up a training program. Australia originally stated a requirement for 72 aircraft, but, in a recent briefing, LM F-35 program chief Lorraine Martin said they would sign for 58.

The near-100 F-35s in the test and training program at six U.S. airbases plus Fort Worth are limited to subsonic flight, 18 degrees AoA and maneuvers from -1g to +3g. Previously, the F-35 was cleared to Mach 1.6, 50 degrees AoA and 7g. Borescope inspections of the front fan section of each P&W F135 engine must be performed after every three hours in the air. At the recent Farnborough Air Show, P&W president Paul Adams said that the latest failure was not related to previous problems with the F135, but P&W has otherwise been tight-lipped about the affair. Assistant Secretary of the Navy Sean Stackley said the F135 is not yet a mature engine, with “only 18,000 flight hours” accumulated. Another 24,000 hours have been amassed in ground tests, a P&W spokesman told AIN. The reliability rate “is not as good as it should be,” admitted P&W’s president for military engines Bennett Croswell at a pre-Farnborough briefing.

It is not yet clear whether the flight restrictions will affect the start of sea trials with the F-35C–already postponed until November this year­–or the goal of completing flight test of the Block 2B software by the end of the year. This is the standard required by the U.S. Marine Corps before its first F-35B squadron can be declared operational. That milestone is due on July 1, 2015.

Program officials say 60 percent of the overall flight-test program has now been done. But the ultimate currently planned software load, designated Block 3F, has yet to begin flight testing. At the same pre-Farnborough briefing, the F-35 Joint Program Office (JPO) chief, Lt. Gen. Chris Bogdan, said Block 3F could be six months late, “but we’ve built margin into the schedule because that last part is really hard.” Bogdan also noted that key F-35 support elements, such as logistics, mission planning and training systems, are behind schedule.

The JPO has not yet completed negotiations with LM for the LRIP 8 batch neither of aircraft, nor with P&W for the LRIP-7+8 engines. “It’s a long process…the Pentagon has raised the standard for FAR Part 15 contracting,” noted Croswell. The lack of agreements has delayed the UK’s commitment to buy 14 F-35Bs for its first squadron. At the recent Farnborough Air Show, former UK Defence Secretary Philip Hammond told AIN that negotiations are continuing. “As you would expect, we’re looking to get the best deal we can for the British taxpayer,” he said.